The present invention relates to a navigation device, and more particularly, to a travel time calculating method and traffic information display technique. Japanese Patent Laid-open Publication No. H10-82644 (hereinafter, referred to as Patent Document 1) discloses a technique in which a display configuration of a predetermined road on a map displayed on a display is changed according to the degree of traffic jam, in a navigation device. For example, in the case where the predetermined road is included in a route searched by route search, a portion of the predetermined road included in the route is displayed according to that degree of traffic jam on the road, which is judged by traffic information collected during a predetermined period of time in the past.